If it would save them money I am sure they would do it. My guess is the cost of the solar panels along with how often they would need to be replaced makes it cost prohibitive right now.
Forgot to mention that every 18 wheeler hauling a box trailer is ripe for a solar panel also.
You may have seen while waiting at a railroad crossing how many 18 wheeler
trailers are being hauled long haul by trains.
Before they are delivered to the truck destination point to haul on the road.
Those sources of electricity can be plugged in to the train while being hauled by trains.
I watched Electrical Engineers design an Integrated Circuit prototype chip
measuring 1/4 inch x 1/4 inch X 1/8 inch tall that set the company back
$360000 .00. to develop.
Once they ran it through the paces and determined it would work ...
it went into mass production.
The final cost to buy the chip if you wanted one ... $15.50.
The Research & Development of the product up front is the cost you have to
recoup to make the damn thing practicable in the first place in order to make
longstanding future profits.
AND TRUST ME , those Integrated Circuit Chips are obsolete in as little as 18 months,
before they have been copied by Chinese and other enterprises.
This is where international patents and copyrights are virtually ignored.
We do the labor ... they copy it ... mass produce it and undercut us.